Natural Flows

By Carol Perkins

Despite the excitement of Butte Environmental Council’s winning the Drought Water Bank lawsuit in March against the State of California, the Department of Water Resources, and 83 water districts, the pressures to increase water transfers remain.

In February the Bureau of Reclamation issued their finding of no significant environmental impact (FONSI) for Federal water transfers. Individual water sellers may forgo their rights to surface water by idling farmland or by substituting groundwater to meet their irrigation needs. In this way, bit by bit, more local water can be pumped to buyers to the south, without adequately studying the cumulative effect on the Tuscan aquifer system.

As a result of increased water transfers, Northern California streams will endure hidden impacts from groundwater pumping. Moving more water out of the natural hydrologic system is a bad deal for Butte County and all the surrounding counties.

The following data identifies the reported through-Delta transfers that moved water from the Northern Sacramento Valley to points south of the Delta in acre-feet/year. This year and next, the Bureau plans to move an additional 215,000 acre-feet out of the Sacramento River Valley. That total includes 110,000 acre-feet of groundwater.

Through-Delta Transfers Sacramento River Region

An acre-foot is equivalent to nearly 326,000 gallons, which is enough water for a household of 4 for a year, where each member consumes 220 gallons per day. Californians on average continue to flaunt water, consuming about 270 gallons per person per day. By comparison Australians are now limited to about 35 gpd. The hydrologic cycle in Queensland is so broken that they have also had to choose to import all their food.

A common thread in our efforts to alter the hydrologic cycle – to deliver water to farmers at times other than when Mother Nature would supply it – is our belief in the capacity of technology to tame nature. The science of engineering allows us, we think, to overcome the limits of nature. (from Water Follies by Glennon)

In the 1950s the Cosumnes River, which flows from the foothills just south of Sacramento, was engineered to flow straighter within man-made levees. The levees isolated the river from its floodplain, starving it of vital recharge capacity, reducing in turn groundwater that would feed the river later in the year. Groundwater pumping further affected the hydrologic system between the river and the aquifer. The pumping amplified the duration of low flows in the fall, which directly affected the spawning Chinook salmon. (1) The resulting impact to the salmon runs was devastating. A river that once was home to substantial fall runs of Chinook saw consistently less than 600 in a season. Under suitable, natural flow conditions this river was capable of supporting up to 17,000 salmon (2) estimated in a 1957 study by the California Department of Fish and Game.

Major cones of depression surround the lower Cosumnes River. Increased reliance on groundwater led to overdraft, calling for management strategies that would address the declining surface and groundwater supplies. A UC Davis team led by Jeff Mount developed a model that predicted a reduction of groundwater pumping on the order of 190,000 acre-feet per year would be required to restore the river’s flows.

It’s hard not to draw similarities between our beleaguered Butte Creek and the Cosumnes River.

The adjacent illustrations show different types of stream aquifer interactions. Conditions A and B can be natural variations due to seasonal or hydrologic changes. While C may also represent natural conditions of an ephemeral system, it is indicative of a dry or arid climate. For Northern California environments, C depicts an unnatural, anthropogenic change related to unsustainable human use of water resources.

Illustrations A and B indicate a change in hydraulic gradient and are representative of many of the streams along the eastern edge of the Sacramento Valley (3). Groundwater feeds the stream in A, usually during the dry season with little to no runoff from snowmelt or rainfall. We find these conditions along our streams in the upper reaches such as Big Chico Creek above Salmon Hole and Butte Creek above the DeSabla Powerhouse.

Our streams depend on groundwater or they will flow too low or dry.

The stream recharges groundwater during periods of high surface flow from runoff of rain events or snowmelt as depicted in B.

Some reaches of the Cosumnes River function similarly to the stream seepage as shown in C, where the stream flows down into the aquifer because of the lowered groundwater table.

Without research it is difficult to understand how stream and aquifer systems interact; likewise, it is difficult to know when and where the system as a whole can become broken as depicted in C. The methods for getting the data are well established, and research is needed to understand the local hydrologic systems.

…effective land and water management requires a clear understanding of the linkages between ground water and surface water as it applies to any given hydrologic setting (4)

The connections between streams and groundwater have been verified in well established studies of disturbed hydrologic systems throughout the world. In California, studies on the Carmel River (5), Mojave River (6), and the Cosumnes River all describe the negative impacts to stream flows from local groundwater pumping. Robert Glennon’s book “Water Follies: Groundwater Pumping and the Fate of America’s Fresh Waters” (2002) also explores the fate of the Cosumnes River and others as well as wetlands, springs, and lakes.

Each hydrologic system differs in the precise ways that the groundwater and surface waters interact. The variables are numerous and complex to assess; however, some of the more accessible information are the types of rock the rivers traverse, the stream stage and the groundwater elevations. The Bureau’s plan for water transfers ignores this complexity in their FONSI. Instead of claiming no significant environmental impact, they should be collecting the data needed to understand the Tuscan aquifer system as a whole.

We need greater focus on protection and conservation of local water resources, and we must demand adequate science that will enable the regional hydrologic cycle to remain largely natural and well managed into the future.

Bibliography

. Fleckenstein, J., et al. Managing Surface Water-Groundwater to Restore Fall Flows in the Cosumnes River, Journal of Water Resources Planning And Management. 2004.

. U.S. Fish and Wildlife Service. Draft anadromous fish restoration plan: a plan to increase natural production of anadromous fish in the Central Valley of California. 1995.

. Graphic found in Chapter 3: Links Between River Flows and Groundwater Conditions of the Cosumnes Research Group phase I project. This report was last accessed on March 24, 2010 at http:// baydelta.ucdavis.edu/reports/crg1?q=reports/crg1/hydrology.

4. Winter, Thomas C., et al. Ground water and surface water: a single resource. U.S. Geological Survey circular – 1139. 1998.

5. Kondolf, G. M., et al. Effects of bank storage and well pumping on base flow, Carmel River, Monterey County, California. Journal of Hydrology, 91:351-369, 1987.

6. Lines, G. C. Ground-water and surface-water relations along the Mojave River, southern California. USGS Water Resources Investigations Report, 95-4189, 1996.

From the Spring 2010 issue of the Environmental News.